1. Field of the Invention
The present invention relates to bucket mechanisms for traffic regulation in a data network.
2. Background Art
A packet communication network accommodates data contained inside packets. Packet traffic, if not regulated, may cause network congestion. During network congestion, packets may be dropped or lost. Traffic regulation techniques attempt to manage network traffic to avoid congestion. Bucket mechanisms are one technique used to regulate traffic at the packet level. Bucket mechanisms include one or more token buckets, leaky buckets, and any other bucket arrangement used for policing and/or shaping data by using tokens or the equivalent thereof.
An existing traffic regulator using a bucket mechanism includes a token bucket. The token bucket receives new tokens at a fixed rate. The maximum number of tokens that the bucket can hold is the bucket depth. If the bucket is already full when a new token is received, the new token is ignored. When a packet arrives at the regulator, a number of tokens equal to the bit size (or byte size in some applications) of the packet must be removed from the bucket for the packet to be sent normally. In the event that there are not enough tokens present in the bucket, the packet is either dropped or remarked with a lower priority and then sent. The rate that new tokens are received at the token bucket defines the maximum sustained normal data rate, while the bucket depth defines the maximum data burst size. The bucket mechanism may optionally include multiple policy support. That is, different classifications of traffic may be regulated by different token buckets such that the token bucket for one class of traffic may be defined differently than the token bucket for another class of traffic.
An existing packet communication network that is used extensively is the Internet. The Internet is a collection of interconnected networks. An Internet service provider (ISP) provides its subscribers access to the Internet. The transmission control protocol/Internet protocol (TCP/IP) family of protocols is used for communication over the Internet. A typical application for a traffic regulator using a bucket mechanism is to locate the traffic regulator at the subscriber's connection to the ISP to regulate downstream data flow (from the ISP to the subscriber). The ISP configures the traffic regulator by defining the bucket mechanism parameters. The parameters remain fixed and are configured according to the subscriber agreement to provide the agreed upon maximum sustained normal data rate in the downstream direction. A suitable technique is used to regulate upstream data transfer.
The ISP typically bills the subscriber for Internet access in a flat rate arrangement that allows unlimited access for a fixed monthly or yearly fee. This arrangement simplifies billing but results in a situation where a small portion of the subscriber base is responsible for a majority of the ISP network costs. That is, a small portion of the subscriber base demands a majority of the network resources.
Accordingly, this flat rate billing arrangement for Internet access typically used by ISP's results in a somewhat inequitable distribution of service costs to the subscribers. These inequities could be addressed by modifying the billing approach. For example, a tiered billing structure or strict usage-based billing could be used to better match the amount billed to a subscriber to the actual subscriber usage. However, in certain situations it may be desirable to stay with flat rate billing. Further, there may be certain situations where modifying the billing approach does not fully address the problem of inequitable service cost distribution.
Background information may be found in U.S. Pat. Nos. 5,289,462 and 6,147,970, and in Cisco IOS Quality of Service Solutions Configuration Guide, Policing and Shaping Overview (Cisco Systems, Inc., May 2003), pages QC-203-QC-218.
For the foregoing reasons, there is a need for an improved traffic regulation method that provides a more equitable distribution of network resources to subscribers.